
respectively. The exotic quantum number \(J^{PC}=1^{-+}\)  and the mass \(M=1855\pm {}9^{+6}_{-1}\)  MeV that the \(\eta _1(1855)\)  possesses proved
strong evidence for \(\eta _1(1855)\)  as a good hybrid state candidate. This is because the existence of a hybrid meson with \(J^{PC}=1^{-+}\) 
and the mass in the 1.8 to 2.1 GeV mass region has been predicted in many early works [1]}, [2]}, [3]}, [4]}, [5]}.
Indeed, many works at present can nature interpret the \(\eta _1(1855)\)  as a hybrid meson. In particular, the QCD axial anomaly supports
the interpretation of the \(\eta _1(1855)\)  as the \(\bar{s}sg\)  hybrid meson [6]}, which was also supported by the Lattice
QCD [7]} and the flux tube model picture [8]}. An additional hybrid meson explanation of the \(\eta _1(1855)\)  can be
found in Ref. [9]}.
